Life is a Struggle...to define.

There was an interesting blog post on a recent meeting of the AAAS - the organization that publishes Science magazine, that you might've missed since it came out on Valentine's Day. But one of the questions that scientists had gathered to address was "If we came across alien life, would we even know it was alive?"

It's an interesting question that emphasizes that we are good at looking for what we already know, and struggle somewhat to define how to look for something we haven't found yet. While this obviously applies to the search for extraterrestrial life in strange places like the hydrocarbon seas of Titan, it also applies to "The Shadow Biosphere" that represents life on earth that we haven't yet discovered.  While the term Shadow Biosphere refers to Life of a fundamentally different nature than DNA-based life, it's worth pointing out that plenty of strange DNA-based life has only been discovered recently: Annamox bacteria, novel microbial communities deep in the ocean and even new viruses of unusual size.

This highlights the fact that when it comes to defining Life, we are best to admit that the definition may change and when it does it will likely be from someone figuring out how to find something super cool.

More on this topic and the origin of life:

1 The cellular/acellular divide
2 Magma oceans and marauding asteroids
3 The First Language
4 The Singularity (x 3)
5 To Catch a Predator